共查询到20条相似文献,搜索用时 31 毫秒
1.
Chow-Choong Ngeow Shashi M. Kanbur 《Monthly notices of the Royal Astronomical Society》2005,360(3):1033-1039
There is strong evidence that the period–luminosity (PL) relation for the Large Magellanic Cloud (LMC) Cepheids shows a break at a period around 10 d. Because the LMC PL relation is extensively used in distance scale studies, the non-linearity of the LMC PL relation may affect the results based on this LMC calibrated relation. In this paper we show that this problem can be remedied by using the Wesenheit function in obtaining Cepheid distances. This is because the Wesenheit function is linear, although recent data suggest that the PL and the period–colour (PC) relations that make up the Wesenheit function are not. We test the linearity of the Wesenheit function and find strong evidence that the LMC Wesenheit function is indeed linear. This is because the non-linearity of the PL and PC relations cancel out when the Wesenheit function is constructed. We discuss this result in the context of distance scale applications. We also compare the distance moduli obtained from μ0 =μ V − R (μ V −μ I ) (equivalent to Wesenheit functions) constructed with the linear and the broken LMC PL relations, and we find that the typical difference in distance moduli is ∼ ±0.03 mag . Hence, the broken LMC PL relation does not seriously affect current distance scale applications. We also discuss the random error calculated with equation μ0 =μ V − R (μ V −μ I ) , and show that there is a correlation term that exists from the calculation of the random error. The calculated random error will be larger if this correlation term is ignored. 相似文献
2.
D. K. Sahu G. C. Anupama T. P. Prabhu 《Monthly notices of the Royal Astronomical Society》2006,366(2):682-688
Optical UBVRI photometry of the type Ia supernova (SN Ia) SN 2002hu covering the period from −2 to +73 d since B maximum is presented. The supernova reached at maximum brightness in B on JD 245 2591.78 ± 0.5 with an apparent magnitude of 16.83 ± 0.02 mag and a relatively blue colour ( B − V ) =−0.08 ± 0.04 mag . The luminosity decline rate of Δ m 15 ( B ) = 1.00 ± 0.05 indicates an absolute B magnitude at maximum of M max B =−19.38 ± 0.3 . The estimated absolute B magnitude, together with the photometric evolution, indicate SN 2002hu was slightly overluminous compared to the average SNe Ia. The distance modulus to the parent galaxy is estimated to be μ= 36.04 ± 0.20 . 相似文献
3.
Piotr Popowski 《Monthly notices of the Royal Astronomical Society》2001,321(3):502-506
I explore the consequences of making the RR Lyrae and clump giant distance scales consistent in the solar neighbourhood, Galactic bulge and Large Magellanic Cloud (LMC). I employ two major assumptions: (i) that the absolute magnitude–metallicity, M V (RR)–[Fe/H], relation for RR Lyrae stars is universal, and (ii) that absolute I magnitudes of clump giants, M I (RC), in Baade's Window are known (e.g. can be inferred from the local Hipparcos -based calibration or theoretical modelling). A comparison between the solar neighbourhood and Baade's Window sets M V (RR) at [Fe/H]=−1.6 in the range (0.59±0.05, 0.70±0.05), somewhat brighter than the statistical parallax solution. More luminous RR Lyrae stars imply younger globular clusters, which would be in better agreement with the conclusions from the currently favoured stellar evolution and cosmological models. A comparison between Baade's Window and the LMC sets M LMC(RC) I in the range (−0.33±0.09,−0.53±0.09). The distance modulus to the LMC is μ LMC ∈(18.24±0.08,18.44±0.07). Unlike M LMC(RC) I , this range in μ LMC does not depend on the adopted value of the dereddened LMC clump magnitude, I LMC(RC) 0 . I argue that the currently available information is insufficient to select the correct distance scale with high confidence. 相似文献
4.
A. K. Dambis 《Monthly notices of the Royal Astronomical Society》2009,396(1):553-569
We use accurate absolute proper motions and Two-Micron All-Sky Survey Ks -band apparent magnitudes for 364 Galactic RR Lyrae variables to determine the kinematical parameters of the Galactic RR Lyrae population and constrain the zero-point of the Ks -band period–luminosity relation for these stars via statistical parallax. We find the mean velocities of the halo- and thick-disc RR Lyrae populations in the solar neighbourhood to be [ U 0 (Halo), V 0 (Halo), W 0 (Halo)]= (−12 ± 10, −217 ± 9, −6 ± 6) km s−1 and [ U 0 (Disc), V 0 (Disc), W 0 (Disc)]= (−15 ± 7, −44 ± 7, −25 ± 5) km s−1 , respectively, and the corresponding components of the velocity-dispersion ellipsoids, [σ VR (Halo), σ V θ (Halo), σ W (Halo)]= (167 ± 9, 86 ± 6, 78 ± 5) km s−1 and [σ VR (Disc), σ V θ (Disc), σ W (Disc)]= (55 ± 7, 44 ± 6, 30 ± 4) km s−1 , respectively. The fraction of thick-disc stars is estimated at 0.25 ± 0.03 . The corrected infrared period–luminosity relation is , implying a Large Magellanic Cloud (LMC) distance modulus of 18.27 ± 0.08 and a solar Galactocentric distance of 7.58 ± 0.40 kpc . Our results suggest no or slightly prograde rotation for the population of halo RR Lyraes in the Milky Way. 相似文献
5.
N. McBride J. K. Davies S. F. Green M. J. Foster 《Monthly notices of the Royal Astronomical Society》1999,306(4):799-805
Minor planet 1997 CU26 is a Centaur, and is probably undergoing dynamical evolution inwards from the Kuiper Belt. We present optical and infrared ( VRIJHK ) photometry which gives mean colours of V − R =0.46±0.02, V − I =1.02±0.02, V − J =1.74±0.02, V − H =2.15±0.02 and V − K =2.25±0.02. The resulting relative reflectance spectrum lies between those of Chiron and Pholus (although closer to that of Chiron). A 1.6–2.6 μm spectrum confirms the broad absorption feature at 2.05 μm associated with water ice reported by Brown et al. 1997 CU26 displays no significant light curve variation and (unlike Chiron) has no observable coma. We place an upper limit to the dust production rate of 1.5 kg s−1 . J -band data taken at phase angles of 1.°7 to 4.°0 give a phase parameter of G J =0.36±0.1, and are consistent with a phase parameter of G =0.15 in the V band (a value often assigned to low-albedo objects when no other information is available) if we assume a phase reddening of 0.017 mag deg−1 in the J band. We find V (1, α =4.°1) =7.022±0.02, from which we deduce, by assuming G =0.15±0.1, an absolute visual magnitude of H V =6.64±0.04. 相似文献
6.
A. E. Dolphin 《Monthly notices of the Royal Astronomical Society》2000,313(2):281-290
Ground-based UBV photometry of two fields in the northern disc of the Large Magellanic Cloud (LMC) is presented. A distance modulus of ( m − M )0 =18.41±0.04 and an extinction of A V =0.30±0.05 have been calculated for these fields. The measurable star formation history of the LMC began no more than 12 Gyr ago with a strong star‐forming episode with [Fe/H]=−1.63±0.10 that accounted for approximately half (by mass) of the total star formation of the LMC in the first 3 Gyr. The data do not give accurate star formation rates during intermediate ages, but there appears to have been a recent increase in the star formation rate in these fields, beginning approximately 2.5 Gyr ago, with the current metallicity in the region being [Fe/H]=−0.38±0.10. The two fields have had very similar star formation rates until 200 Myr ago, at which point one shows a large increase. 相似文献
7.
Andrés E. Piatti Juan J. Clariá Andrea V. Ahumada 《Monthly notices of the Royal Astronomical Society》2003,346(2):390-402
Charge-coupled device (CCD) photometry in the Johnson V , Kron–Cousins I and Washington CMT 1 systems is presented in the field of the poorly known open cluster NGC 2627. Four independent Washington abundance indices yield a mean cluster metallicity of [Fe/H]=−0.12 ± 0.08 , which is compatible with the existence of a radial gradient in the Galactic disc. The resultant colour–magnitude diagrams indicate that the cluster is an intermediate-age object of 1.4 Gyr. Based on the best fits of the Geneva group's isochrones to the ( V , V − I ) and ( T 1 , C − T 1 ) diagrams, we estimate E ( V − I ) = 0.25 ± 0.05 and V − MV = 11.80 ± 0.25 for log t = 9.15 , and E ( C − T 1 ) = 0.23 ± 0.07 and T 1 − M T 1 = 11.85 ± 0.25 for log t = 9.10 , respectively, assuming solar metal content. The derived reddening value E ( C − T 1 ) implies E ( B − V ) = 0.12 ± 0.07 and a distance from the Sun of 2.0 ± 0.4 kpc . Using the WEBDA data base and the available literature, we re-examined the overall properties of all the open clusters with ages between 0.6 and 2.5 Gyr. We identified peaks of cluster formation at 0.7–0.8, 1.0–1.1, 1.6–1.7 and 2.0–2.1 Gyr, separated by relative quiescent epochs of ∼0.2–0.3 Gyr. We also estimated a radial abundance gradient of −0.08 ± 0.02 , which is consistent with the most recent determinations for the Galactic disc, but no clear evidence for a gradient perpendicular to the Galactic plane is found. 相似文献
8.
Neil Trentham R. Brent Tully Marc A. W. Verheijen 《Monthly notices of the Royal Astronomical Society》2001,325(3):1275-1280
We present and discuss optical, near-infrared and H i measurements of the galaxy Markarian 1460 at a distance of 19 Mpc in the Ursa Major Cluster. This low-luminosity ( M B =−14) galaxy is unusual because (i) it is blue ( B − R =0.8) and has the spectrum of an H ii galaxy, (ii) it has a light profile that is smooth and well fitted by an r 1/4 and not an exponential function at all radii larger than the seeing, and (iii) it has an observed central brightness of about μ B =20 mag arcsec−2 , intermediate between those of elliptical galaxies (on the bright μ B side) and normal low-luminosity dwarf irregular (on the low μ B side) galaxies. No other known galaxy exhibits all these properties in conjunction. On morphological grounds this galaxy looks like a normal distant luminous elliptical galaxy, since the Fundamental Plane tells us that higher luminosity normal elliptical galaxies tend to have lower surface-brightnesses. Markarian 1460 has 2×107 M⊙ of H i and a ratio M (H i )/ L B of 0.2, which is low compared to the typical values for star-forming dwarf galaxies. From the high surface-brightness and r 1/4 profile, we infer that the baryonic component of Markarian 1460 has become self-gravitating through dissipative processes. From the colours, radio continuum, H i and optical emission line properties, and yet smooth texture, we infer that Markarian 1460 has had significant star formation as recently as ∼1 Gyr ago but not today. 相似文献
9.
Raffaele G. Gratton 《Monthly notices of the Royal Astronomical Society》1998,296(3):739-745
Hipparcos satellite parallaxes for 22 metal-poor field horizontal branch stars with V 0 <9 are used to derive their absolute magnitude. The weighted mean value is MV =+0.69±0.10 for an average metallicity of [Fe/H]=−1.41; a somewhat brighter average magnitude of MV =+0.60±0.12 for an average metallicity of [Fe/H]=−1.51 is obtained by eliminating HD 17072, which might be on the first ascent of the giant branch rather than on the horizontal branch. The present values agree with the determinations based on proper motions and application of the Baade–Wesselink method to field RR Lyraes; they are 0.1–0.2 mag fainter than those based on calibration of cluster distances obtained by using local subdwarfs and on alternative distance calibrators for the Large Magellanic Cloud (LMC). The possibility that there is a real difference between the luminosity of the horizontal branch for clusters and the field is briefly commented on. 相似文献
10.
We present HST /WFPC2 observations of UGC 4483, an irregular galaxy in the M81/NGC 2403 complex. Stellar photometry was carried out with HSTphot, and is complete to V ≃26.0 and I ≃24.7. We measure the red giant branch tip at I =23.56±0.10, and calculate a distance modulus of μ 0 =27.53±0.12 (corresponding to a distance of 3.2±0.2 Mpc), placing UGC 4483 within the NGC 2403 subgroup. We were able to measure properties of a previously known young star cluster in UGC 4483, finding integrated magnitudes of V =18.66±0.21 and I =18.54±0.10 for the stellar contribution (integrated light minus H α and [O iii ] contribution), corresponding to an age of ∼10–15 Myr and an initial mass of ∼104 M⊙ . This is consistent with the properties of the cluster's brightest stars, which were resolved in the data for the first time. Finally, a numerical analysis of the galaxy's stellar content yields a roughly constant star formation rate of 1.3×10−3 M⊙ yr−1 and mean metallicity of [Fe/H]=−1.3 dex from 15 Gyr ago to the present. 相似文献
11.
Iskren Y. Georgiev Thomas H. Puzia Michael Hilker Paul Goudfrooij 《Monthly notices of the Royal Astronomical Society》2009,392(2):879-893
We investigate the old globular cluster (GC) population of 68 faint ( M V > −16 mag) dwarf galaxies located in the halo regions of nearby (≲12 Mpc) loose galaxy groups and in the field environment based on archival Hubble Space Telescope ( HST )/Advanced Camera for Surveys (ACS) images in F606W and F814W filters. The combined colour distribution of 175 GC candidates peaks at ( V − I ) = 0.96 ± 0.07 mag and the GC luminosity function turnover for the entire sample is found at M V ,TO =−7.6 ± 0.11 mag , similar to the old metal-poor Large Magellanic Cloud (LMC) GC population. Our data reveal a tentative trend of M V ,TO becoming fainter from late- to early-type galaxies. The luminosity and colour distributions of GCs in dIrrs show a lack of faint blue GCs (bGCs). Our analysis reveals that this might reflect a relatively younger GC system than typically found in luminous early-type galaxies. If verified by spectroscopy, this would suggest a later formation epoch of the first metal-poor star clusters in dwarf galaxies. We find several bright (massive) GCs which reside in the nuclear regions of their host galaxies. These nuclear clusters have similar luminosities and structural parameters as the peculiar Galactic clusters suspected of being the remnant nuclei of accreted dwarf galaxies, such as M54 and ωCen. Except for these nuclear clusters, the distribution of GCs in dIrrs in the half-light radius versus cluster mass plane is very similar to that of Galactic young halo clusters, which suggests comparable formation and dynamical evolution histories. A comparison with theoretical models of cluster disruption indicates that GCs in low-mass galaxies evolve dynamically as self-gravitating systems in a benign tidal environment. 相似文献
12.
Andrés E. Piatti Juan J. Clariá Andrea V. Ahumada 《Monthly notices of the Royal Astronomical Society》2009,397(2):1073-1083
We present CCD photometry in the Johnson U , B and V and Kron–Cousins I passbands for the open cluster NGC 2587. The sample consists of 4406 stars reaching down to V ∼ 21.0 . We developed a new method to clean statistically the colour–magnitude diagrams. NGC 2587 appears to be a sparse, relatively bright open cluster, with a few tens of members projected on to a populous star field. The comparatively bright F7/8 II type star HD 70927, located close to the cluster centre, seems not to be a member. Our analysis suggests that NGC 2587 is slightly younger than the Hyades and probably of solar metallicity. A cluster radius of roughly 8 arcmin was estimated from the radial stellar density profile. From 18 probable cluster members with measured proper motions, we derive the following mean values for NGC 2587: μα =−4.3 ± 3.6 mas yr−1 and μδ =−2.5 ± 3.4 mas yr−1 . Adopting the theoretical metal content Z = 0.02 , which provides the best global fit, we derive a cluster age of 500+60 −50 . Simultaneously, colour excesses E ( B − V ) = 0.10 and E ( V − I ) = 0.15 and an apparent distance modulus of V − MV = 12.50 are obtained. The interstellar extinction in the cluster direction is found to follow the normal law. NGC 2587 is located at a distance of (2.70 ± 0.70) kpc from the Sun and ∼9.8 kpc from the Galactic centre. 相似文献
13.
Michael Zemcov Mark Halpern Colin Borys Scott Chapman Wayne Holland Elena Pierpaoli Douglas Scott 《Monthly notices of the Royal Astronomical Society》2003,346(4):1179-1188
We have detected the Sunyaev–Zel'dovich (SZ) increment at 850 μm in two galaxy clusters (Cl 0016+16 and MS 1054.4−0321) using the Submillimetre Common User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. Fits to the isothermal β model yield a central Compton y parameter of (2.2 ± 0.7) × 10−4 and a central 850-μm flux of Δ I 0 = 2.2 ± 0.7 mJy beam−1 in Cl 0016. This can be combined with decrement measurements to infer y = (2.38 ±0.36 0.34 ) × 10−4 and v pec = 400±1900 1400 km s−1 . In MS 1054 we find a peak 850-μm flux of Δ I 0 = 2.0 ± 1.0 mJy beam−1 and y = (2.0 ± 1.0) × 10−4 . To be successful such measurements require large chop throws and non-standard data analysis techniques. In particular, the 450-μm data are used to remove atmospheric variations in the 850-μm data. An explicit annular model is fit to the SCUBA difference data in order to extract the radial profile, and separately fit to the model differences to minimize the effect of correlations induced by our scanning strategy. We have demonstrated that with sufficient care, SCUBA can be used to measure the SZ increment in massive, compact galaxy clusters. 相似文献
14.
F. Donato G. Gentile P. Salucci C. Frigerio Martins M. I. Wilkinson G. Gilmore E. K. Grebel A. Koch R. Wyse 《Monthly notices of the Royal Astronomical Society》2009,397(3):1169-1176
We confirm and extend the recent finding that the central surface density μ0D ≡ r 0 ρ0 of galaxy dark matter haloes, where r 0 and ρ0 are the halo core radius and central density, is nearly constant and independent of galaxy luminosity. Based on the co-added rotation curves (RCs) of ∼1000 spiral galaxies, the mass models of individual dwarf irregular and spiral galaxies of late and early types with high-quality RCs, and the galaxy–galaxy weak-lensing signals from a sample of spiral and elliptical galaxies, we find that log μ0D = 2.15 ± 0.2 in units of log(M⊙ pc−2 ) . We also show that the observed kinematics of Local Group dwarf spheroidal galaxies are consistent with this value. Our results are obtained for galactic systems spanning over 14 mag, belonging to different Hubble types and whose mass profiles have been determined by several independent methods. In the same objects, the approximate constancy of μ0D is in sharp contrast to the systematical variations, by several orders of magnitude, of galaxy properties, including ρ0 and central stellar surface density. 相似文献
15.
Maurizio Salaris Susan Percival Léo Girardi 《Monthly notices of the Royal Astronomical Society》2003,345(3):1030-1038
We present a detailed analysis of the uncertainty on the theoretical population corrections to the Large Magellanic Cloud (LMC) red clump (RC) absolute magnitude, by employing a population synthesis algorithm to simulate theoretically the photometric and spectroscopic properties of RC stars, under various assumptions concerning the LMC star formation rate (SFR) and age–metallicity relationship (AMR). A comparison of the outcome of our simulations with observations of evolved low- to intermediate-mass stars in the LMC allows one to select the combinations of SFR and AMR that bracket the real LMC star formation history, and to estimate the systematic error on the associated RC population corrections.
The most accurate estimate of the LMC distance modulus from the RC method (adopting the OGLE-II reddening maps for the LMC) is obtained from the K -band magnitude, and provides ( m − M )0,LMC = 18.47 ± 0.01(random)+0.05 −0.06 (systematic) . Distances obtained from the I band, or from the multicolour RC technique which determines at the same time reddening and distance, both agree (albeit with a slightly larger error bar) with this value. 相似文献
The most accurate estimate of the LMC distance modulus from the RC method (adopting the OGLE-II reddening maps for the LMC) is obtained from the K -band magnitude, and provides ( m − M )
16.
F. Caputo V. Castellani M. Marconi V. Ripepi 《Monthly notices of the Royal Astronomical Society》2000,316(4):819-826
We use the results from recent computations of updated non-linear convective pulsating models to constrain the distance modulus of Galactic globular clusters through the observed periods of first-overtone (RR c ) pulsators. The resulting relation between the mean absolute magnitude of RR Lyrae stars 〈 M V (RR)〉 and the heavy element content [Fe/H] appears well in the range of several previous empirical calibrations, but with a non-linear dependence on [Fe/H] so that the slope of the relation increases when moving towards larger metallicities. On this ground, our results suggest that metal-poor ([Fe/H]<−1.5) and metal-rich ([Fe/H]>−1.5) variables follow two different linear 〈 M V (RR)〉−[Fe/H] relations. Application to RR Lyrae stars in the metal-poor globular clusters of the Large Magellanic Cloud (LMC) provides an LMC distance modulus of the order of 18.6 mag, thus supporting the 'long' distance scale. The comparison with recent predictions based on updated stellar evolution theory is briefly presented and discussed. 相似文献
17.
Patricia A. Whitelock Michael W. Feast Floor van Leeuwen 《Monthly notices of the Royal Astronomical Society》2008,386(1):313-323
Published data for large-amplitude asymptotic giant branch variables in the Large Magellanic Cloud (LMC) are re-analysed to establish the constants for an infrared ( K ) period–luminosity relation of the form M K =ρ[log P − 2.38]+δ . A slope of ρ=−3.51 ± 0.20 and a zero-point of δ=−7.15 ± 0.06 are found for oxygen-rich Miras (if a distance modulus of 18.39 ± 0.05 is used for the LMC). Assuming this slope is applicable to Galactic Miras we discuss the zero-point for these stars using the revised Hipparcos parallaxes together with published very long baseline interferometry (VLBI) parallaxes for OH masers and Miras in globular clusters. These result in a mean zero-point of δ=−7.25 ± 0.07 for O-rich Galactic Miras. The zero-point for Miras in the Galactic bulge is not significantly different from this value.
Carbon-rich stars are also discussed and provide results that are consistent with the above numbers, but with higher uncertainties. Within the uncertainties there is no evidence for a significant difference between the period–luminosity relation zero-points for systems with different metallicity. 相似文献
Carbon-rich stars are also discussed and provide results that are consistent with the above numbers, but with higher uncertainties. Within the uncertainties there is no evidence for a significant difference between the period–luminosity relation zero-points for systems with different metallicity. 相似文献
18.
To study the kinematics of O-B5 giant stars (luminosity class III), 290 non-Gould belt stars with proper motions taken from the Hipparcos catalogue are used, of which 107 have radial velocities taken from other sources. Semidefinite programming solves for the kinematical parameters and the coefficients of the velocity ellipsoid. The condition that both solutions must yield the same solar velocity is enforced. The results obtained are reasonable: solar velocity of 13.83 ± 0.17 km s−1 ; Oort's constants, in units of km s−1 kpc−1 , A = 16.08 ± 0.72 and B =−10.74 ± 0.65, implying a rotational velocity of 228.0 ± 21.4 km s−1 if we take the distance to the Galactic Centre as 8.5 ± 1.1 kpc; velocity dispersions, in units of km s−1 , of σ x = 32.44 ± 5.04, σ y = 26.16 ± 2.75, σ z = 18.71 ± 2.39 with a vertex deviation of 相似文献
19.
D. P. Kjurkchieva D. V. Marchev S. Zola 《Monthly notices of the Royal Astronomical Society》2007,382(2):835-839
High-resolution spectroscopic observations around the Hα line of the binary star QX Cas covering the whole orbital period are presented. Our radial velocity solution, the first ever determined, requires an eccentric orbit with the following orbital parameters: eccentricity, e = 0.22 ± 0.01 ; longitude of periastron, ω= 45°± 5° ; semi-amplitudes of the radial velocity curves of the primary and secondary stars, K 1 sin i = 125.8 ± 0.9 km s−1 and K 2 sin i = 144.8 ± 1.1 km s−1 ; gamma velocity, V 0 = 65.1 ± 0.5 km s−1 ; and mass ratio, q = 0.869 ± 0.013 . The corresponding lower limits of the masses of the components and their separation are , and a sin i = 31.34 ± 0.48 R⊙ . 相似文献
20.
M. J. Pierce J. S. Jurcevic D. Crabtree 《Monthly notices of the Royal Astronomical Society》2000,313(2):271-280
We present CCD photometry of red supergiant long-period variables (LPVs) in the Per OB1 association, the Large Magellanic Cloud (LMC) and M33. The photometry was obtained in the Kron–Cousins R and I bandpasses and in a narrow bandpass ( λ 0 =8250 Å, FWHM=300 Å) chosen to avoid TiO bands in the spectral energy distribution of the LPVs. Because the strength of the TiO bands varies greatly with temperature, which varies with the phase of an LPV, avoiding TiO reduces the amplitude of the photometric variations seen in LPVs. The result is a lower dispersion and a well defined period–luminosity (PL) relation.
For the LMC sample we find an rms dispersion of 0.27 mag in the narrow-band PL relation and slightly larger dispersions for the LPVs in Per OB1 and M33. This dispersion is comparable to that of the Cepheid PL relation at similar wavelengths. Adopting a distance modulus of 18.5±0.1 mag for the LMC, we obtain distance moduli of 11.68±0.15 mag for Per OB1 and 24.85±0.13 mag for M33. These distances agree well with those based on main sequence fitting for Per OB1 and the Cepheid distance for M33. Since LPVs are ∼ 5 times more common than Cepheids and have a well defined PL relation, LPVs provide a promising method for estimating Galactic and extra galactic distances. 相似文献
For the LMC sample we find an rms dispersion of 0.27 mag in the narrow-band PL relation and slightly larger dispersions for the LPVs in Per OB1 and M33. This dispersion is comparable to that of the Cepheid PL relation at similar wavelengths. Adopting a distance modulus of 18.5±0.1 mag for the LMC, we obtain distance moduli of 11.68±0.15 mag for Per OB1 and 24.85±0.13 mag for M33. These distances agree well with those based on main sequence fitting for Per OB1 and the Cepheid distance for M33. Since LPVs are ∼ 5 times more common than Cepheids and have a well defined PL relation, LPVs provide a promising method for estimating Galactic and extra galactic distances. 相似文献